#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <math.h>

struct Point 
{
    int x;
    int y;
};

int main() 
{
    struct Point z1, z2;
    scanf("%d %d", &z1.x, &z1.y);
    scanf("%d %d", &z2.x, &z2.y);
    double distance = sqrt(pow(z1.x - z2.x, 2) + pow(z1.y - z2.y, 2));
    printf("distance = %.2lf", distance);
    return 0;
}